14 A REVISION OF THE ASTACID^. 



curiously modified so as to resemble the same jDarts in the males of the 

 genus Astacus. The transverse suture near the base of the appendage is 

 obliterated ; the apical half, instead of being membranous and fringed with 

 setae, as in tlie normal female, is firm and naked, and rolled from the out- 

 side inward so as to form on the inner side a groove which is converted into 

 a tube just at the tip, owing to the closeness of the coil at that point. The 

 whole oruran is larcfer and thicker than in the ordinary female, althouorh not 

 so large as in the male. The tip is altogether destitute of tlie recurved hooks 

 of the normal male organ in this species. 



The fourth specimen belongs to C. propmqnus Girard. It is 72 milli- 

 meters long (M. C. Z., No. 3432). It agrees with the female in every respect 

 except the shape of the first pair of abdominal limbs, which are partly trans- 

 formed into the condition which obtains in the male. The modification of 

 the appendages has not gone so far on the right side as on the left. In both, 

 the transverse suture is obliterated ; the basal half is thick and corneous, 

 and produced into a prominent tubercle on the inner side, as in the male. 

 The apical half of the right appendage retains the membranaceous and 

 setiferous character of the female appendage, while in the left it is more 

 corneous, and rolled from without inwards in such a fashion as to form an 

 inner and an outer part somewhat as in the male, though neither part is 

 in this case produced into an acute style, as in the normal male, and the 

 outer part retains the membranaceous setiferous tip. 



These specimens are in such a bad state of preservation that a deter- 

 mination of the sex from the internal generative organs in several of 

 them is wellnigh impossible. Dissection of the first-described specimen, 

 with the orifices of the generative organs in the base of the last pair of legs, 

 as in the male, revealed many large ovarian eggs, and I little doubt that 

 the other three individuals are females which have assumed some of the 

 characters of the opposite sex.* It would be interesting to determine from 

 fresh specimens whether such monstrous conditions as those just described 

 ever denote true hermaphrodites, producing both male and female genera- 

 tive elements, or whether they may involve sterility. They ai'e the more 

 interesting from the fact that hermaphroditism exists as a normal condition 

 in another highly specialized order of Crustacea, the Isopoda.f 



* Boas (Vidcusk. Sclsk, Skr. 6te Riickke, iialurvidciisk. og Math. Afd., Bd. I. pp. 9i, 1S4) says lie lias 

 seen a female Thaliisuna anomala and a female Antaeus Jluviatilis with abdominal appendages like tiie male, 

 but gives no particulars concerning these specimens. 



t See Bullar, Journ. Anat. Physiol., Vol. XI. p. 118, 1S76; Ann. JIag. Nat. Hist., 4th Scr., Vol. XIX. 

 p. 254, 1877; and P. Mayer, Mitth. Zoolog. Station zu Neapcl, Vol. I. pp. 165, 177, 1878. 



